/*
 * @(#)BasicConstraintsExtension.java	1.20 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program is distributed in the hope that it will be useful, but  
 * WITHOUT ANY WARRANTY; without even the implied warranty of  
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package sun.security.x509;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.reflect.Array;
import java.util.Enumeration;

import sun.security.util.*;

/**
 * This class represents the Basic Constraints Extension.
 *
 * <p>The basic constraints extension identifies whether the subject of the
 * certificate is a CA and how deep a certification path may exist
 * through that CA.
 *
 * <pre>
 * The ASN.1 syntax for this extension is:
 * BasicConstraints ::= SEQUENCE {
 *     cA                BOOLEAN DEFAULT FALSE,
 *     pathLenConstraint INTEGER (0..MAX) OPTIONAL
 * }
 * </pre>
 * @author Amit Kapoor
 * @author Hemma Prafullchandra
 * @version 1.13
 * @see CertAttrSet
 * @see Extension
 */
public class BasicConstraintsExtension extends Extension
implements CertAttrSet {
    /**
     * Identifier for this attribute, to be used with the
     * get, set, delete methods of Certificate, x509 type.
     */
    public static final String IDENT = "x509.info.extensions.BasicConstraints";
    /**
     * Attribute names.
     */
    public static final String NAME = "BasicConstraints";
    public static final String IS_CA = "is_ca";
    public static final String PATH_LEN = "path_len";

    // Private data members
    private boolean	ca = false;
    private int	pathLen = -1;

    // Encode this extension value
    private void encodeThis() throws IOException {
        if (ca == false && pathLen < 0) {
            this.extensionValue = null;
            return;
        }
        DerOutputStream out = new DerOutputStream();
        DerOutputStream tmp = new DerOutputStream();

        if (ca) {
            tmp.putBoolean(ca);
        }
        if (pathLen >= 0) {
            tmp.putInteger(pathLen);
        }
        out.write(DerValue.tag_Sequence, tmp);
        this.extensionValue = out.toByteArray();
    }

    /**
     * Default constructor for this object. The extension is marked
     * critical if the ca flag is true, false otherwise.
     *
     * @param ca true, if the subject of the Certificate is a CA.
     * @param len specifies the depth of the certification path.
     */
    public BasicConstraintsExtension(boolean ca, int len) throws IOException {
	this(new Boolean(ca), ca, len);
    }

    /**
     * Constructor for this object with specified criticality.
     *
     * @param critical true, if the extension should be marked critical
     * @param ca true, if the subject of the Certificate is a CA.
     * @param len specifies the depth of the certification path.
     */
    public BasicConstraintsExtension(Boolean critical, boolean ca, int len) 
    throws IOException {
        this.ca = ca;
        this.pathLen = len;
        this.extensionId = PKIXExtensions.BasicConstraints_Id;
        this.critical = critical.booleanValue();
        encodeThis();
    }

    /**
     * Create the extension from the passed DER encoded value of the same.
     *
     * @param extension the DER encoded value of the extension.
     * @exception IOException on error.
     */
     public BasicConstraintsExtension(Boolean critical, Object value)
	 throws IOException
    {
         this.extensionId = PKIXExtensions.BasicConstraints_Id;
	 this.critical = critical.booleanValue();

         if (value instanceof byte[]) {
             int len = Array.getLength(value);
             byte[] extValue = new byte[len];
             System.arraycopy(value, 0, extValue, 0, len);

             this.extensionValue = extValue;
             DerValue val = new DerValue(extValue);
             if (val.tag != DerValue.tag_Sequence) {
                 throw new IOException("Invalid encoding of BasicConstraints");
             }

             if (val.data == null) {
		 // non-CA cert ("cA" field is FALSE by default), return -1
                 return;
             }
             DerValue opt = val.data.getDerValue();
             if (opt.tag != DerValue.tag_Boolean) {
		 // non-CA cert ("cA" field is FALSE by default), return -1
		 return;
             }

	     this.ca = opt.getBoolean();
	     if (val.data.available() == 0) {
		 // From PKIX profile:
		 // Where pathLenConstraint does not appear, there is no
		 // limit to the allowed length of the certification path.
		 this.pathLen = Integer.MAX_VALUE;
		 return;
	     }

	     opt = val.data.getDerValue();
             if (opt.tag != DerValue.tag_Integer) {
                 throw new IOException("Invalid encoding of BasicConstraints");
             }
             this.pathLen = opt.getInteger();
             /*
              * Activate this check once again after PKIX profiling
              * is a standard and this check no longer imposes an
              * interoperability barrier.
              * if (ca) {
              *   if (!this.critical) {
              *   throw new IOException("Criticality cannot be false for CA.");
              *   }
              * }
              */
          } else
              throw new IOException("Invalid argument type");
     }

     /**
      * Return user readable form of extension.
      */
     public String toString() {
         String s = super.toString() + "BasicConstraints:[\n";

         s += ((ca) ? ("CA:true") : ("CA:false")) + "\n";
         if (pathLen >= 0) {
             s += "PathLen:" + pathLen + "\n";
         } else {
             s += "PathLen: undefined\n";
         }
         return (s + "]\n");
     }

    /**
     * Decode the extension from the InputStream.
     *
     * @param in the InputStream to unmarshal the contents from.
     * @exception IOException on decoding or validity errors.
     */
    public void decode(InputStream in) throws IOException {
        throw new IOException("Method not to be called directly.");
    }

     /**
      * Encode this extension value to the output stream.
      *
      * @param out the DerOutputStream to encode the extension to.
      */
     public void encode(OutputStream out) throws IOException {
         DerOutputStream tmp = new DerOutputStream();
         if (extensionValue == null) {
             this.extensionId = PKIXExtensions.BasicConstraints_Id;
             if (ca) {
	         critical = true;
             } else {
	         critical = false;
             }
             encodeThis();
         }
         super.encode(tmp);

	 out.write(tmp.toByteArray());
     }

    /**
     * Set the attribute value.
     */
    public void set(String name, Object obj) throws IOException {
	if (name.equalsIgnoreCase(IS_CA)) {
	    if (!(obj instanceof Boolean)) {
	      throw new IOException("Attribute value should be of type Boolean.");
	    }
	    ca = ((Boolean)obj).booleanValue();
	} else if (name.equalsIgnoreCase(PATH_LEN)) {
	    if (!(obj instanceof Integer)) {
	      throw new IOException("Attribute value should be of type Integer.");
	    }
	    pathLen = ((Integer)obj).intValue();
	} else {
	  throw new IOException("Attribute name not recognized by " +
				"CertAttrSet:BasicConstraints.");
	}
        encodeThis();
    }

    /**
     * Get the attribute value.
     */
    public Object get(String name) throws IOException {
	if (name.equalsIgnoreCase(IS_CA)) {
	    return (new Boolean(ca));
	} else if (name.equalsIgnoreCase(PATH_LEN)) {
	    return (new Integer(pathLen));
	} else {
	  throw new IOException("Attribute name not recognized by " +
				"CertAttrSet:BasicConstraints.");
	}
    }

    /**
     * Delete the attribute value.
     */
    public void delete(String name) throws IOException {
	if (name.equalsIgnoreCase(IS_CA)) {
	    ca = false;
	} else if (name.equalsIgnoreCase(PATH_LEN)) {
	    pathLen = -1;
	} else {
	  throw new IOException("Attribute name not recognized by " +
				"CertAttrSet:BasicConstraints.");
	}
        encodeThis();
    }

    /**
     * Return an enumeration of names of attributes existing within this
     * attribute.
     */
    public Enumeration getElements() {
        AttributeNameEnumeration elements = new AttributeNameEnumeration();
        elements.addElement(IS_CA);
        elements.addElement(PATH_LEN);

	return (elements.elements());
    }

    /**
     * Return the name of this attribute.
     */
    public String getName() {
        return (NAME);
    }
}
